Skip to main content
Ctrl+K
Astropy v7.2.0 - Home Astropy v7.2.0 - Home
  • Getting Started
  • User Guide
  • Contributing
  • Project Details
  • Learn
  • Packages
  • GitHub
  • Getting Started
  • User Guide
  • Contributing
  • Project Details
  • Learn
  • Packages
  • GitHub

Section Navigation

Data structures and transformations

  • Constants (astropy.constants)
  • Units and Quantities (astropy.units)
  • N-Dimensional Datasets (astropy.nddata)
  • Data Tables (astropy.table)
  • Time and Dates (astropy.time)
  • Time Series (astropy.timeseries)
  • Astronomical Coordinate Systems (astropy.coordinates)
  • World Coordinate System (astropy.wcs)
  • Models and Fitting (astropy.modeling)
  • Uncertainties and Distributions (astropy.uncertainty)

File I/O

  • Overview of Astropy File I/O
  • High-level Unified File I/O
  • FITS File Handling (astropy.io.fits)
  • Text Tables (astropy.io.ascii)
  • VOTable Handling (astropy.io.votable)
  • ECVS, HDF5, Parquet, PyArrow CSV, YAML (astropy.io.misc)

Computations and utilities

  • Cosmological Calculations (astropy.cosmology)
    • Included Cosmology Realizations
    • Units and Equivalencies
    • Cosmology I/O & Convert
    • Traits
    • For Developers
    • Reference/API
  • Convolution and Filtering (astropy.convolution)
  • IERS data access (astropy.utils.iers)
  • Data Visualization (astropy.visualization)
  • Astrostatistics Tools (astropy.stats)
  • Masked Values and Quantities (astropy.utils.masked)
  • SAMP (Simple Application Messaging Protocol) (astropy.samp)

Nuts and bolts

  • Configuration System (astropy.config)
  • I/O Registry (astropy.io.registry)
  • I/O Typing (astropy.io.typing)
  • Logging system
  • Python warnings system
  • Astropy Core Package Utilities (astropy.utils)
  • Environment variables
  • Astropy Glossary
  • User Guide
  • Cosmological Calculations (astropy.cosmology)
  • Cosmological Units and Equivalencies
  • with_H0

with_H0#

astropy.cosmology.units.with_H0(H0=None)[source]#

Convert between quantities with little-h and the equivalent physical units.

Parameters:
H0python:None or Quantity [:ref: ‘frequency’]

The value of the Hubble constant to assume. If a |Quantity|, will assume the quantity is H0. If None (default), use the H0 attribute from |default_cosmology|.

References

For an illuminating discussion on why you may or may not want to use little-h at all, see https://arxiv.org/pdf/1308.4150.pdf

previous

redshift_temperature

next

with_redshift

Edit

© Copyright 2011–2025, The Astropy Developers.

Created using Sphinx 8.2.3.

Built with the PyData Sphinx Theme 0.16.1.